Yak-1
M-105PA was built in special variant during winter season
1941-
1942.
Harsh conditions of Russian Winter are very demanding not only on troops, but on any type of equipment,
and special measures are to be taken to keep aircraft in high combat readiness and allow to perform service
in open field conditions. Foreseeing those problems already in Summer
1941,
the GKO (August 14) ordered the
NKAP to design, produce and present to the
VVS universal (except the top side fairing)
ski design suitable for LaGG-3, MiG-3 and
Yak-1. All had to be done in two weeks timeframe.

Corresponding order from NKAP followed next day to
A.S.Yakovlev
for a good reason: Yakovlev's first prototype I-26-1 passed the factory trials
on snow covered field, equipped with skis.

Main ski, designed at
Yakovlev KB
was of 2-spar design, 62x165cm2 size. Weight of a pair was 123kg. Tail ski was also retractable,
same for all types of fighters. Weight - 6kg.

Winter variant of Yak-1 was a series production
aircraft with changes to landing gear and powerplant,
painted with winter camouflage. Analysis of those changes is presented below:

Landing Gear: wheels were replaced by retractable skis. Despite original
fighter design was developed without such a conversion in ming, modification was performed without
major airframe changes. Even the leg and retraction system remained unchanged. During retraction,
skis were raised tight to the ex-wheels wells, proturbing 600mm in front of the wing leading
edge. This part of the ski had special fairing, providing smooth match with the wing surface.

Positive results

Negative results

Ski-fitted Yak-1 could operate from snow-covered fields without special cleaning
or rolling the landing strip.

Lowered center of gravity (heavy skis!) made landing much easier and safer - Yak-1
trend to noseover was temporary cured.

Landing gear weight was increased by 50kg.

Skis themselves as well as the gaps between ski and wing created extra drag,
decreasing aircraft speed by 20 to 30km/h.

Large traction increased takeoff run of the aircraft.

During continuous parking, snow sticks to the ski surface.

Ski undersurface lasted only for 70 to 80 takeoff/landing cycles.

Powerplant: oil and water system elements (tubes, tanks, filters)
under the engine cowling were provided with heat-preserving wrapping. Special system was
responsible for liquefying the oil using the gasoline. Water was replaced by antifreeze,
capable to handle frigid winter temperatures. Aircraft was supplied to airforce with set
of cotton-filled blankets and plugs ('pillows'), specially shaped to cower the propeller
spinner, engine, radiators and air intakes.

Positive results

Negative results

Engine could be quickly started 'cold' under any temperature conditions;

Engine could stay warm for a long time without necessity to run it frequently;

20kg of takeoff weight added;

Camouflage: Winter Variant of Yak-1 was painted with white
glue-based washable paint right over the standard summer camouflage.

Positive results

Negative results

Parked aircraft became almost undetectable from the air.

4 to 5kg of takeoff weight added;

Rough paint surface consumed 7 to 10km/h of speed. But some sanding of the
surface allowed to reclaim this loss easily.

Flight technic of the ski-fitted Yak-1 did not differ from the standard
aircraft. But combat use of ski-equipped fighters proved to be a failure. Luftwaffe operated
their fighters on wheels all the year around, and speed losses of Soviet fighters did not
compensate for some airfield advantages.

Some 830 Yak-1's were fitted with ski landing gear in period from September
1941
to February 25,
1942,
when the concept was finally disregarded. Since
1942
ski-fitted fighters saw only limited service with the North Front regiments.

Rejection of the ski undercarriage put stricter demands on the airfield
preparation and increased workload on the BAO.
Special tools had to be developed and produced, but it was necessary to return combat
performance to the combat planes.

Different concept surfaced later, when test-pilot of NIIVVS B.K.Kondratiev proposed so called 'takeoff skis'. Those
skis were not attached to the aircraft and did not help during landing. This solution found limited use
only, mostly to transport damaged aircraft within airfield or from the scene of emergency landing.